In the old days it used to be only the lords of the manor were allowed to keep pigeons. They built the DoveCotes for them, cylindrical shaped buildings mostly with the holes in the upper section leading to nestboxes which were accessed from the inside of the cote.
Later on, the common people began to keep pigeons for food & sport. This is where people started developing the larger meat breeds of pigeons for food, and the smaller, more compact ones for flying and racing. Eventually came the development of the fancier breeds for showing and pets.
If you set up your coop for the birds you will want to get young, unflown birds as your initial breeding stock. Once you get them home and settled in to your loft, you can start allowing them their freedom. If you get older breeder birds, especially Homers and in some cases Rollers and Tipplers, if you let them loose they will try and head back for their old loft. They will have to be kept captive and have a flight attached to the loft for them to fly and exercise in.
Most of your meat type pigeon breeds, such as Kings, Modenas, Runts, Giant Homers, are not good flyers and are pretty much like chickens. Needing low nests and runs for them, they will forage somewhat, but mostly are kept caged.
Homers, will provide a squab about the size of a cornish game hen, maybe a little bit bigger. You harvest them at about 30 days of age while they still have some pin feathers under their wings and before they really start to fly.
The only thing you have to worry about feral pigeons is that they may bring disease into your loft. Otherwise, you will find that your birds may bring back some of the feral ones with them, or you may lose some of your birds to the feral flock.
Pigeons like a higher nesting site than chickens, so your idea of building higher is a good one.
For more information, go to The National Pigeon Website.
Http://www.NPA.org